Air conditioning system



Nov. 26, 1940. G. M. K|NGJSLAND 2,223,287

AIR CONDITIONING SYSTEM Filed June 18, 1958 2 Sl'leebS-Sheei'I l v zf sz sa 'fo sa 34 2,7 E

Il# s B'rwentor S02 @waage Mollmgsllaslmdl NOV. 26, 1940. G, M KlNGsLAND Y 2,223,287

AIR CONDITIONING SYSTEM Filed June 18, 1938 2 Sheets-Sheet 2 nventor Patented Nov. 2e, 1940 PATENT OFFICE 2,223,287 an. ooNnrrioNrNo SYSTEM George M. Kingsland, Minneapolis, Minn., as-

signor to Minneapolis-Honeywell Regulator Company, of Delaware Minneapolis, Minn., a corporation Application June 1s, 193s, serial No. 214,609

12 Claims.

This invention relates to an air conditioning system and more particularly to a system wherein air is circulated through an air conditioning chamber and a space or spaces to be conditioned.

One of the objects of my invention is the provision of a'system of the type above described wherein a variable capacity blower' means is provided for circulating conditioned air through a space or spaces and the capacity of the blower means is regulated in accordance with the static pressure at the outlet of the pressure means.

More particularly it is an object of my invention to provide a zone air conditioning system wherein the flow of air into the various zones is of the air in the various zones, wherein `a blower means is placed in operation Whenever air is admitted into any one of the various zones, and wherein the capacity of the blower means is regulated in accordance with the pressure existing at the outlet of the blower means so that as the number of zones .to which air is admitted increases the blower means will be caused to D- erate at increasing capacity.'

Another object of my invention is the provision of a variable capacity blower means for causing a iiow of conditioned air into a space or spaces to be conditioned, wherein means rethe blower means regulates the capacity of the blower means in such a manner that when the pressure drops toa predetermined low value the blower means will operate at high capacity and when the pressure rises to a high predetermined value the blower means will operate at low capacity, there being a substantial difference in the pressures at which the blower means goes from low to high capacity and vice versa so as to prevent hunting of the blower means.

Other objects and advantages will become apparent upon a study of the specification, claims, and appended drawings wherein like reference characters represent like parts in the various views, and wherein Figure 1 is a schematic view of one form of system embodying my invention,v

Figure 2 is a modification of the system shown in Figure 1, and

Figure 3 is a further modification of the sys- 00 tem of Figure4 1.

Referring now to Figure 1, a portion of an air conditioning chamber is represented by the reference character I0, this chamber containing any suitable form of air conditioning apparatus for conditioning air`which flows therethrough, the

" controlled by means responsive to the condition.

sponsive to the pressure existing at the outlet of air being drawn through this chamber by a fan II driven by a variable speed motorrl2, the 'air passing from the fan I I lthrough a duct I3 which communicates with branch ducts I4, I5, and I6 which direct the air into the spaces I8, I9, 5 and 20,to be conditioned. While only three such spaces are shown it will vbe understood that any number of spaces may be connected to the outlet of the fan. Located in the outlet of the ducts I 4, I5, and I6 are dampers such as the damper 10 22 for controlling the ow of air into the various, spaces. These dampers are operatively connected to motors 25 by means of arm 26 connected vto the damper, a link 21 and an arm 28 connected to the motor. two positional reversible motors provided with terminals 3l), 3|, and 32. Power may be supplied to these motors by means of conductors 33 and 34 connected to any suitable source of power (not shown). 'Ihe arrangement is such that when the terminals 30 and 3l are connected together .the motor 'will rotate the arm 28 in a counterclockwise direction, thus moving the damper 22 to open position as illustrated by the arrows shown in connection withl the motor controlling 2o the damper for the space I8. When the terminals 3l and 32 are connected together the motor will operate to rotate the arm 28 in the reverse direction thus moving the dampers 22 back to closed position.

Any suitable means responsive to the condition of the air in the various spaces may be provided for controlling the operation of these motors but for purposes of illustration I have shown thermo- P stats 35 comprising bimetallic elements 3l carry- 30 ing an arm 38 for movement between spaced contacts 39 and W.

Assuming for theA present that the system is a heating system, when the temperature of the air in the space drops to a predetermined value the arm 38 is moved by the bimetallio element 31 into engagement with the contact 39 and upon an increase in temperature in the space to a high predetermined value the arm 38 is moved into engagement with the contact 40. 'I'he arm 38 is connected by means of a conductor 42 with the terminal 3i of the motor and the contacts 39 and'll are connected by means of conductors t3 and 44 with the terminals 30 and 32, respectively. -It will now be apparent that upon a drop 00 in temperature in any one of the spaces to a predetermined value the arm 38 of the thermostat in that particular space will move into engagement with the contact 39 and cause operation of the motor to move the damper 22 controlling These motors may be 15 the ow of air into that space into open position. Upon a rise in temperature in the space the arm 38 moves into engagement with the contact 40 and the motor 25 then causes closing movement of the damper 22. If the system ls to be used as a cooling system instead of a heating system the thermostat would be so arranged so as to cause movement of the arms 38 in the opposite direction in response to rise and fall of temperatures `in the spaces or else the connections to the' Asion of the links 21 and these switches are arranged so as to close when the dampers are moved to an open position, and these switches are all connected in parallel byA means of the conductors 52 and 53 to the conductors 54 and 55, respectively, and control the energization of a relay generally indicated by the reference character 56. This relay comprises a relay coil 51, and an armature 58'connected to a switch arm 59 which cooperates with av xed contact 60. The arrangement is such that upon energization of the coil 51 the arm 59 is moved into engagement with the contact 60 and when the relay coil 51 is deenergized, the arm 59 moves out of engagement with the contact 60 under the infiuence of gravity or any suitable biasing means. A step-down transformer 62 is provided for supplying power to the relay coil 51, this transformer including a high tension primary 63 connected across line 'wires 64 and 65 which are connected to a suitable source of power (not shown), and a low tension secondary 66. The conductor 55 is connected to one side of the secondary 66 and the conductor 68 connects the other side of the secondary with one side of the rel-ay coil 51. The conductor 54 is connected to Athe other side of the relay coil 51 and it will now be apparent that whenever any one of the mercury switches 50 are moved to closed position by the opening of the damper controlled by the particular motor with which the switch is associated, the conductors 54 and 55 are connected together so that current flows through the relay coil 51 as follows: from one side of the secspeed motor and a starting box 10 of any sultable construction is provided for causlng'the operation of the motor upon the establishment of certain circuit connections to be hereinafter described. Terminals 1| and 12 are connected to the source of power and form the ,low speed starter terminals for the motor i2. The terminals 13 and 14 on the load side of the starter 10 connect to the low speed terminal 15 and 15 of the motor. The terminals 11 and 18 form the high speed terminals on the starter box 10 which are to be suitably connected to the source of power and the terminals 60 and 8| on the load side of this starter connect to the high speed terminals 82 and 83 of the motor I2.

. Connected by means of a pipe 85 is a static pressure responsive device 86 which may be 'of4 any conventional construction but is shown as comprising a pair ofchambers 88 and 89 which are separated by a suitable pressure responsive diaphragm (not shown) and to this diaphragm is connected a plunger 90 which moves through the top portion of the chamber 89 in response to variations in the static pressure in the outlet duct I3. Pivoted to a projection 92 which is formed on the outside of the casing of the pressure responsive member 86 is a bell crank lever 93 which includes an arm 94 biased by spring 96 into engagement with the plunger 90 and an arm 98 suitably insulated from the rest of the lever and arranged to sweep across a potentiometer resistance 99. Upon an increase in pressure in the discharge duct i3 the plunger 90 moves upwardly and causes movement of the arm 98 to the right asviewed in Figure 1 and upon a decrease in pressure the arm 98 will beicaused to be moved to the left under the influence of the biasing spring 96.

The potentiometer 99 forms `-the control potentiometer for a proportioning motor |02. This motor may be of any suitable construction and may be of the type illustrated in Patent 2,026,110 issued toA D. G. Taylor on Jan. 14, 1936. The motor |02 is provided with terminals |03, |04,

and |05 connected by means of conductors |06,

|01, and |08, respectively, to the left and right ends .oi the potentiometer resistance 99 and to the control arm 98, respectively. The motor |02 is connected to the line wires 64 and 65 by mean's of the conductors ||2 and` ||3 anda shaft ||4 is arranged to be vdriven by the motor |02. It will be understood upon a study of the Taylor patent above mentioned that the shaft ||4 will rotate to positions corresponding to the position of the control -arm 98 with respect to the potentiometer resistance 99.

Carried by the shaft ||4 of the motor |02 are a pair of cams ||8 and ||9, these cams controlling the positions of switch arms |20 and |2|, respectively. Switch arm |20 cooperates with a xed contact |22 and the arm |2| cooperates with a fixed contact |23. The arrangement is such that as the arm 98 moves towards the right, the shaft ||4 rotates the cams ||8 and ||9 in a clockwise direction and the switch arm |20 will drop/out of engagement with the' contact |22 after the cam has movedthrough a predetermined angle and subsequently upon continued rotation of the shaft ||4 in .the same direction the cam 9 will have rotated far enough to allow the `arm |2| to move out of engagement with the contact |23. Movement of the arm 98 from the right end of the resistance 99 toward the left will cause reverse movement of the cams ||8 and ||9 and arm |2| will first be moved into engagement with the contact |23 and then the arm |20 will be moved into engagement with the contact |22. A relay |30 is provided for controlling the high lspeed circuit to the motor |2, this relay being the arms move into engagement with the respective contacts upon energization of the relay coil |3| and upon deenergization thereof they move out of engagement with their respective contacts under the influence of gravity or any suitable biasing means.

Operation When the syste-m is ilrst startedA in operation and power is supplied to line wires 60 and 65, if the condition in all the spaces it at a desirable value and the various dampers are shut so that the mercury switches are in open position the motor' |2 will be deenergized and the static pressure will be at a low value so that the control arm 98 will be in the position illustrated. 'I'he relays' 50 and |30 will be deenergized and all the parts will be in the positions illustrated. Assume now that the condition in one of the spaces attains an undesirable value so that the damper 22 for that particular space moves to open position and the associated mercury switch 50 moves to closed position, relay 56 will then be energized as previously described and this in turn will cause energization of the low speed terminals of the motor l2 as follows: from the line wire 65 through conductor |40, contact 60, arm 50, conductor |4|, terminal 12 of the starter box 10, terminal 1|, and conductor |43 to the line 64. Power now being supplied to the terminals 1| and 12, the motor l2 will be caused to operate at low speed. When the fan is rst started up it will be understood that the static pressure is `low so that the arms |20 and |2| are in engagement with their respective contacts. Relay |30 is therefore energized through the following circuit: from the load side of the starter box through conductor |45, Contact |23, arm |2|, conductors |46, |41, arm |20, contact |22, conductors |48', |40, relay coil 3|, and conductor |50 back to the load terminal 14 of the, starter box 10. Energization of the relay |30 causes movement of arms |33 and |34 into engagement with their respective contacts and power is now supplied to the high speed terminals 11 and 18 of the box 10 as follows: from the line wire 65 through conductor |55, arm |33, contact |35, conductor |56, terminal 18 of the starter box 10, terminal 11 and conductor |51 back to the line wire 64. The motor is now caused to operate at high speed. The movement of arm |34 into engagement with contact |36 energizes a maintaining circuit for the relay coil |3| which is independent of engagement of arm |20 with contact |22, this circuit being as follows: from terminal 13 through conductor |45, contact |23, arm |2|, conductors |46, |60, arm |34, contacts -ment with the contact |23.v

If only one of the dampers 22 has been opened, the pressure in the discharge duct |3 will rapidly increase and after it reaches a certain high value the cam ||8 will have been rotated suiciently far by the motor |02 to permit arm |20 to move out of engagement with the contact |22. As previously stated, however, the relay will not be deenergized by this but will remain energized until ythe pressure builds up to a higher lpredetermined value whereupon the motor |02 causes cam I9 to move far enough to permit arm I2 to move out ci engagement with the contact |23. The relay |30 is now deenergized and the circuit to the high speed terminals of the motor I2 is interrupted by reason of the arm |33 moving out of engagement with the contact |35. The motor now drops back to low speed whereupon the static pressure in the discharge duct vi3 begins to drop and arm 98 moves toward the left with respect to resistance 90 and the motor |02 will cause rotation of shaft H0 and the cams M3 and H0 in 'a counter-clockwise direction. Switch arm |2| will rst move into engagement with contact H23 but the relay |30 cannot be energized until the other switch arm |20 moves into engagement with contact |22. This cannot take place until the pressure drops to a low predetermined value which may not take place as long as only one of the dampers 22 is open. If an increasing number of spaces require a fiowof conditioned air thereto, the dampers for these spaces will open whereupon the pressure in the discharge duct will drop and when a suiiicient number of these spaces are calling for conditioned air the pressure will drop sufficiently far so that the switch arm |20 will be moved by the cam ||0 into engagement with the contact |22 and the relay |30 will be reenergized as set forth above thus causing operation of the motor l2 on high speed again and increasing the amount of air circulated by the fan H.

By reason of the arrangement of switches |20 and |2| controlling the relay 30 the motor l2 goes on to high speed only when the static pressure drops to a low predetermined value and goes on to low speed only when the static pressure increases to a high predetermined value and there is a suilicient difference in pressure between thesel values so that the fan motor will not hunt by reason of small pressure variations in the discharge duct |3.

It will now be seen that the speed of the motor I2 will depend upon the pressure in the discharge duct |3 which in turn will depend upon the number of dampers in the ducts |4, l5, and I6 that are in open position and when all these dampers move to closed position indicating that no conditioned air is necessary in any of the spaces the relay 56 drops out thus deenergizing the motor I2 and shutting the fan down entirely. This is a distinct advantage over systems wherein the fan runs continuously regardless of the necessity for supplying conditioned air to the various spaces and wherein dampers placed ahead of the fan vary the amount of air circulated by the fan in accordance with the demand on the system since my arrangement results in increased econ omy and operating eiliciency. i

Description of Figure 2 Referring now to Figure 2 the zones or spaces to be conditioned have not been illustrated but the relay 56 is again provided and it will be unv derstood that the energization of this relay is controlled by the dampers for the various spaces in exactly the same manner as in Figure 1. In other words, upon opening of any one of these dampers the relay coil 51 will be energized and the arm 59 will be moved into engagement with the contact 60. l

In place of the two-speed motor I2 for operating a fan I3, a pair of fans |10 and |1| are connected in parallel to the discharge duct 3 and the air conditioning chamber l0 and motors |12 and |13 are provided for operating these fans. The amount of air that is circulated through the chamber |0 and theV discharge duct I3 is controlled by controlling the number of these motors which is in operation. When the relay 56 is energized poweris supplied to the motor |13 as follows: from the line wire 64 through the contact 60, arm 59, conductors |15 and |16 to the.

starter box |80, and thence back to the line wire 65 by means of the'conductor I8I. Accordingly as long as anyl one space is demanding a supply of conditioned air the motor |13 will operate the fan |1I. A The operation of the motor |12 is controlled by means of a relay 200, this relay including a pair of opposed balanced coils and 202. An armature 203 is controlled by these coils and this armature controls the position of arms 204 and 205 with relation to the contacts 206 and 201. Upon energization of the coil 20| the arms 204 and 205 move into engagement with their respective contacts and upon deenergization of the coilthe arms move away from their respective contacts under the inuence of gravity or any suitable biasing means.

The energization of the relay 200 is controlled by the pressure controller 86 which may be of the same construction as shown in Figure 1y except that in place of the bell crank lever 93 having the arm 98 moving over resistance 99, an arm 2 l0 pivoted to the projection 92 and biased by means of the spring 96 into engagement with the plunger 90 is provided, this arm being movable between spaced contacts 2|2 and 2I3. When the pressure in the discharge duct I3 is low the arm 2|0 is in engagement with the contact 2i2 and when the pressure inthe duct I3 increases to a high predetermined value the arm 2|0 is moved into engagement with'the contact 2|3. Power is v supplied to the relay 200 by means of a stepdown transformer 220, this transformer including a high tension primary 22| connected across the line wires 64 and 65 and a low tension secondary 222. Power tothe transformer `220 is controlled by the relay 56, this transformer being energized as will be readily apparent when the arm 59 operated by the relay moves into engagement with the contact 60.

When the transformer 220 is energized and the pressure in the discharge duct is suficiently low so that the arm 2|0 of the pressure responsive device 86 is in engagement with-the contact 2|2 the relay coil 20| will be energized through the following circuit: from thetransformer secondary 222 through lconductors 230, 23|, contact 2|2,

. so thatthe relay coil will not be deenergized upon a slight increase in pressure and movement of the arm 2|0 out of engagement with the contact 2|2. This maintaining circuit is as follows: from the transformer secondaryv 222` through conductors 230, 238, contact 206, arm 204, conductors 230, 234, relay coil 20|, conductors 235 and 236 to the other side of the secondary 222. Accordingly, once the relay 200 is energized by engagement of arm 2|0 with the contact 2|2 it will remain energized even after the arm 'moves out of engagement with the contact2 I 2.

When the arm 205 moves into engagement with the contact 201 the fan motorv |12 is energized as follows: from the load side of the starter box |80 through conductor 242, motor terminal 243 Tthrough the motor which may have built into it a starter coil (not shown) similar to the starter box |80, through the motor to terminal 244, con- 'ductor 245, contact 201, arm 205, and conductor 248 to the other terminal on the load side of the starter box |80. Operation of both of the fans |10 and I1I will now cause the pressure in the duct I3 to increase and if only one or a small number of the dampers 22 are opened the pressure will increase to such a value that the arm 2|0 of the pressure responsive device 86 will move into engagement with 'the contact 2I3 which will result in the deenergization of the relay 200 as follows: current ows from the transformer secondary 222 through the conductors 230, 238, contact 206, arm 204, conductors 239, 233, the arm 2|0, contact 2I3, conductor 250 through the coil 202 and conductor 236 to the other side of the secondary 222. The energization of coil 202 which has an opposing or bucking action with respect to the coil 20| permits movement ofy the armature 203 and the switch arms 204 and 205 to the right under the iniiuence of gravity or any suitable biasingV means, thus breaking the holding circuit for the coil '20| at the contact 206. 'It should be noted that the circuit through the relay coil 202 alsoincluded this contact 206 so that as soon as the arm 204 moves away from this contact both of the relay coils are deenergized and will remain deenergized-until the'pressure in the discharge duct I3 drops to a low enough value so that the arm 2|0 moves back into engagement with the contact 2 I 2. v

It will thus be seen that the amount of air which is circulated through the discharge duct I3 is controlled in accordance with the static pressure therein inthe same manner as in Figure 1 except that the variation in the amount of air circulated is controlled by providing two motor fan units instead of a two-speed motor as in Figure l. The provision of the relay 200 in place of motor |02 and its associated cams and switches for controlling the operation of the motor |12 provides for a definite operating diierential in the same manner as in Figure 1 but eliminates the necessity of providing a separate motor for controlling theI motor |12. It should be understood of course that this relay could be substituted for the motor |02 and the associated cams and switches in the system of Figure 1 and conversely the two-speed motor of Figure 1 could be replaced b'y the two motors |12 and |13 of Figure 2. The operation of the systems in these L,

Description of Figure 3 Referring now to the form of invention shown in Figure 3 the particular zones, the condition responsive device therein, and the dampers for controlling the flow of air into the various zones have been omitted inthis figure as in Figure 2 for the sake of simplicity. A relay 56 similar to the relay of Figure 1 and operated in the same manner as in Figures 1 yand 2 is provided for controlling the supply of power to the line Wires 64 and 65. A pair of fans 260 and 26| connected in parallel to the discharge duct I3 and the air conditioning chamber I0 are provided, these fans being operated by a small low speed motor 262 and a larger high speed motor 263, respectively.

When the motor 262 is alone operating the flow ofl air through the duct I3 is at its lowest value, when the motor 263 is operating alone, the iiow of air through the duct I3 is at a higher value and if both motors are operating together the flow of ,air to the duct I3 is at a maximum value.

escaner The motor 263 is controlled by a relay 216 which may be similar in construction to the relay 260 of Figure 2 this relay including opposed coils 21| and 212, an armature 213, and switch arms 214 and 215. Cooperating with the arm 214 is a contact 216 which is engaged thereby `lirhen the relay is energized and cooperating with the arm 216 is a contact 211 which is engaged thereby when the relay is energized. Upon deenergization of the relay, the arms move out oi' engagement with the contacts 216 and 211, respectively, and the arm 215 moves into engagement with a second lcontact 218. A step-down transformer 266 having a primary 28| connected across vthe line wires 64 and 65 and a secondary 262 is provided for energizing the relay 216.

The energization of the relay 21|) is controlled by the cam H9 operating the.switch arm.|2| as in Figure 1,this arm moving between the spaced contacts |23 and the contact 36|). This -cam together with the ca m H8 operating the switch arm |26 isv mounted on the shaft H4 operated by the proportioning motor |62 which is in turn controlled by the pressure responsive device 68 which, for purposes of illustration, have been illustrated as being identical with those of Figure 1. When the pressure in the duct i3 is at a low value the cams I I3 and |I9 are in the positions illustrated and the arms |20 and 2| are in engagement with the contacts |22 and |23, respectively. As the pressure'in the duet i3 increases the cams rotate clockwise and arm |26 is first moved'out of engagementwith contact |22. As the pressure in the duct I3 rises still further to a higher predetermined rvalue, the cam H6 allows the arm I2I to move out of engagement with the contact |23 and by reason of the curvature of the cam, upon an increase in pressure to a still higher value, the arm I2I moves into engagement with the other contact 360.

` Operation of Figure 3 As in Figures 1 and 2, upon a call for conditioned air in any oneA or'more of the zones, the

relay 56 is energized and the arm 69 is moved 315 and 3I6. The arm |2| being at this time in engagement with the contact |23, the relay coil 21| of the relay 216 is energized as follows: from the transformer secongary 282 through conductors 326, 32|, contact |23, a`rm |21, conductors 624, coil 21|, conductors 325 and 326 to the other side of the secondary 282. Relay coil 21| being energized, lthe arms 214.and 216 are moved into engagement with the contacts 216 and 211. Engagement of contact 216 by the arm 214 complates a maintaining circuit for the relay coil 21| which does not depend upon engagement of the arm |2| with the contact |23, this circuit being as follows: from the transformer secondary 262 through conductors 32|), 330, arm 214, contact 216, conductor 33|, relay coil 21|, conductors 325 and 326 to the other side of the secondary 282. The engagement of contact 211 by the arm 215 causes they large ian motor 262 to he energized as iollows: from the line wire 64 through conductor 346, arm 216, contact 211, conductor 34|motor 263, and conductors 342 and 316 back to the linewire 66. Accordingly with thepressure in the discharge duct at ar low value both the contacts |22 and |23 are engaged by the arms |26 and |21 and the motors 262 and 263 are both energized thus causing a maximum :How of air through the discharge duct "I3, it be- 5 ing understood of course that the relay 56 is energized by reason of the factthat one or more of the dampers 22 arein open position.

Should the pressure in the discharge duct |3 rise to .a high enough value so that the motor |62 causes movement of canr |113 sufiicientlyfar to cause the `arm |26 to move out of engagement with the contact |22 the circuit to the motor 262 is interrupted since the previously described circuit for this motor included this contact and the small fan motor 262 is now placed out of operation. The amount oi air owing through the discharge yduct 12 is now decreased as Will be understood.

If the pressure in the discharge duct I3 continuesvto rise and the motor i112 moves the cam. |19 suiciently far so as to move the arm I2| into engagement with the contact 366 upon a rise in pressure to a predetermined value, the relay 210 is deenergized by rst energizing the coil 212 through the previously described maintaining cswitch for this relay as follows: from the transformer secondary 262 through conductors 320, 236, arm 216, contact 216, conductors 331,324, arm |21, contact 366, conductor 356, the coil 212, and conductor 626 to the other side of the secondary 262. Energization of the coil 212 counteraets the effect of the coils 21| on the armature 213 whereupon the arms 212 and 216 move out of engagement with contacts 216 and 211 and 35 the arm 216 moves into engagement with the contact 212. The circuit to the tor 263 is inter- ,rupted but ya new circuit is now established through the motor 262 .as follows: from the. line wire 64 through conductor 666,'switch arm 215, 40 conductors 266, tit through the motor 262 and conductors 316 and 216 to the line wire 65. The small motor 262 is nowagain placed in operation while the large motor 266 is placed out of operation and the fan 266 now operates at its slower speed to discharge air through the duct I3 at a. minimum rate.

It will therefore be vapparent that the rate of ciow of the air through the duct i3 will depend upon whether one or the other or both of the motors 262 and 262 are in operationand that these motors are controlled by the cams |16 and H9 which are operated by the motor |62 -in response to the pressure air in the duct i3. When. all the zone i m1. are closed and relay 61 is 55 deenergized neither of the' motors 262 or 263 will operate. Whenever one or more oi' the zone dempers are open however and the relay 61 is energized the motors will operatein accordance with the pressure in the discharge-duct. *When the pressure is at a high value the motor 262 alone operates. When the pressure drops to a lowerv value'as when additional zone dempers are opened i the motor 266 will he placed in operation and the motor 262 will be placed out of operation. 65 Upon a further drop in the static pressure in the duct I3 as may be occasioned by the opening vof still more zone dampers, both of the motors262 and 263 will omrate to circulate a maximunr Ain turn will be varied as the number of zone dampers varies but when all of the zone dampers are closed no air whatever will be circulated by the fan or fans so that there will be noexpenditure of energy bythe fan motor or motors when the condition in all of the zones is satisfactory and there is no need for the supply. of conditioned air thereto.

Having described a preferred form of` my invention many modifications may become apparent to those skilled in the art and I therefore wish it to be understood that my invention is limited only by the scope of the appended claims.

I claim as my invention: Y f

l. In a zone air conditioning system, an air conditioning chamber, variable speed blower means for causing a ow of 'air from the air conditioning chamber into the various zones tobe conditioned, damper means for controlling the now of air into the various zones, motor means for moving the damper means for each zone into open or closed positions, fa plurality of circuit controlling means, means responsive to movement of any of said circuit controlling means to a first position for causing operation of said blower means, means operatively connecting each of said circuit controlling means with one ot said motors so that the circuit controlling means is moved to said first position when the respective motor means has moved its damper means toI open position, means responsive to the condition of the air in the various zones for controlling the operation of the respective motor means,'second circuit controlling means for controlling the speed of the blower means, and means responsive to the pressure of the air at the outlet of the blower means for controlling said second circuit controlling means.

2. In an air conditioning system, variable capacity air circulating means for circulating air into a space to be conditioned, a pair of switch means for controlling the capacity of said air circulating means, means responsive to movement of both of said switch means to a first circuit controlling position for causing operation of the air circulating means at high capacity, means responsive to movement of both of said switch means to a second circuit controlling position for causing operation of the air circulating means at low capacity, and means responsive to the pressure at the discharge side of said air circulating means for causing sequential movement ci said switch means to the first circuit controlling position in response to a decrease in pressure to a first predetermined value and for causing sequential movement of said switch means to the second Icircuit controlling position in response to an increase in pressure to a second predetermined value.

3. In an air conditioning system, variable ca pacity air circulating means for circulating-air into a space to be conditioned, a pair of switch means for controlling the capacity of said air circulating means, means responsive to movement of both of said switch means to a first circuit controlling position for lcausing operation of the air circulating means at high capacity, means responsive to movement of both of said switch means to a second circuit controlling position for causing operation of the air circulating means at low capacity, means responsive to the pressure at the discharge side of said air circulating means for causing sequential movement of said switch means to the rst circuit controlling position in response to a decrease in pressure to a flrst predetermined valuel 'and for causing sequential movement of said switch means to the second circuit controlling position in response -to an increase in pressure toa second predetermined value, damper means for controlling the ow of air into said space, and means responsive to movement of said damper means to open position to place said air circulating means under the control of said condition responsive means.

4. In an air conditioning system, an air conditioning chamber, means for circulating air through said chamber and through a space to be conditioned, said means including a plurality of blowers, damper means for controlling the ow of air into said space, means responsive to a condition of said space for controlling the operation of said damper means, means responsive to the opening of said damper means for causing operation of at least one of said blowers, and means responsive to the pressure at the outlet of said circulating means for controlling the number of said blowers in operation.

5. In a zone air conditioning system, an air conditioning chamber, means for causing a flow of air from said chamber into the various zones i to be conditioned, said means comprising a low capacity blower and a high capacity blower, means responsive to the condition' of the air in the various zones for controlling the supply of air into the respective zones, means for causing operation of the low capacity blower means in response to operation of the air supply controlling means to permit the ow of air into any one of said zones, means responsive to a drop in pressure at the outlet of the blower to a predetermined value for interrupting operation of said low capacity blower and causing operation of said high capacity blower, and means responsive to a drop in pressure at the outlet of the blower to a second predetermined value for causing operation of both of said blowers. v

6. In an air conditioning system, variable -capacity air circulating means for circulating air into a space to be conditioned, relay means controlling the operation of said air circulating means, means for controlling the admission of air into said space, means responsive to operation of said last named means in a manner to permit the admission of air into said space for placing the air circulating means under the control of said relay means, means for causing said air circulating means to operate at low capacity in response to the deenergization of said relay means, means responsive to energization of said relay means to cause operation of said air circulating means at high capacity, means responsive to the pressure at the outlet of said air circulating means, and means controlled by said pressure responsive means to cause energization ofv said relay means when the pressure drops to a low predetermined value and to cause -deenergization of the relay means when the pressure rises 45 combination, variable capacity delivery means -of said spaces for placing said blowers under the control of said relay means, means responsive to energization of said relay means to cause operation of at lea-st two blowers, means responsive to deenergization of said relay means to cause operation of a minimum number of said blowers, means responsive to the pressure at the outlet of said blowers, and means controlled by said pressure responsive means to cause energization of said relay means when the pressure drops to a low predetermined value and to cause deenergization of the relay means when the pressure rises to a high predetermined value.

8. In an air conditioning system, an air conditioning chamber, means for circulating air through said chamber and` through a space to be conditioned, said means comprising a plurality of blowers of varying capacities, means responsive tothe pressure at the outlet of the air circulating means for causing operation of diierent `blowers and for controlling the number of blowers in operation according to a predetermined schedule, means for controlling the admission ,of air into said space, and means for placing the blowers under the control of the condition responsive means in response to operation of the air admission 'controlling means to permit the iiow of air into said space.

9. A pressure control system comprising in combination, variable capacity delivery means for delivering a medium under pressure, pressure responsive means movable in response to pressure changes in said medium caused by said delivery means, and means including a pair of switches operated by said pressure responsive means for controlling the capacity of said delivery means, said two switches cooperating to change operation of said delivery means when in operation from a iirst capacity to a second capacity, and

` 40 one of said switches being capable of maintaining said delivery means in operation at said second capacityv independently of the other of said switches.

10. A pressure control system comprising, in

for delivering a medium under pressure, pressure responsive means movable in responseto pressure changes in said medium caused by said delivery means, a first switch operated by said pressure responsive means for'closing -a circuit to cause a change in capacity of said delivery means When in f operation from a first capacity to a second capacity, a second switch for maintaining said second capacity operation of said delivery means after said nrst switch opens, said.J rst switch being incapable of initiating said second capacity operation of said delivery means indei pendently of saidsecond switch, and condition responsive means for opening and closing a circuit to render said delivery means operative and inoperative.

11. In an air conditioning system, in combination, an air conditioning chamber, variable capacity air circulating means for circulating air through said chamber and through a space to be conditioned, damper means for controlling the flow of air into said space, means responsive to the condition of the space for controlling. the operation of said damper means, means responsive to the opening of said damper means for causing operation of said circulating means, means responsive to the pressure at the outlet of said circulating means for controlling the capacity of said circulating means, and means associated with said last named means for causing said circulating means to operate at a high capacity upon beginning operation thereof,at a low capacity when said circulating means is in operation and the pressure attains a predetermined high value, and at the high capacity when said circulating means is in operation and the'l pressure drops to a predetermined low i-value, there being a substantial difference in these two pressure values whereby hunting of the air circulating means is prevented.

12. In a zone air conditioning system, in combination, an air conditioning chamber, delivery means for circulating air through said chamber and through the various zbnes to be conditioned, damper mean-s associated with each zone for controlling the delivery of air thereto, condition responsive means in each zone for controlling said damper means, first control means controlled by said condition responsive means for rendering said delivery means operative when at least one of said damper means is in open position and inoperative when al1 of said damper means are in closed position, pressure responsiveA means positioned in accordance with pressure changes caused by the closure of onel or more of said I damper means, a rst control device operated by said pressure responsive means for varying the air supplyto lsaid Zones from a rst to a Second of varying the air supply from said second to said j nrst capacity, and a second control device for incapable of varying the air supply from said first to said second capacity,

GEORGE IVI. mNGSLAND.

capacity, said rst control device being incapable 

